add collision demo in readme

refactor: use broad phase optimization in 'update'

fix: tuple<int, int, int> doesn't have hash function, so had to use this instead

add GridPartition member and constructor

update tests

refactor PhysicsWorld class

add broad phase collision optimization

add operator functions to some structs

feat: add PhysicsWorld class

move collision detection and response to the top of the loop

update constructor to accept new parameter

add isDynamic struct member, to know if rigid body is affected by gravity

change RESTITUTION_CO t 0.78f

update CMakeLists

update README